I take it from the German language in game that you are on a EU server ? In which case you shouldn't be using any version of nUI after 5.06.21. The later versions are for the new 3.3.5 patch that introduced chat frame changes that we have had to apply to nUI for the US servers.

Go back to the download page and choose archive and download and install the 5.06.21 version as the latest version for 3.3.3.